This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
鄄 combines 垔 with the village radical ⻏. The exact historical development is uncertain, and the character is rare in modern Japanese.
Since the meaning is unclear, focus on the shape: a village (⻏) beside a component 垔 that looks like a piled structure. Picture an ancient, forgotten village whose name is lost.
For ケン, imagine a forgotten village named Ken: Ken -> ケン, and the village (⻏) is all that remains of the old name.
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